Homeopathy and Evidence-Based Medicine: Back to the Future – Part I

—Scottish homeopath David Reilly at the 2001 Harvard Medical School Complementary and Integrative Medicine Conference.

Reilly based that assertion on his own series of four small studies of homeopathic treatments of hay fever, asthma, and allergic rhinitis, the outcomes of which had been inconsistent and largely subjective. (1) Later he explained that small-minded skeptics in “conventional medicine” assume “homeopathy doesn’t work because it can’t work,” a view echoed by conference host Dr. David Eisenberg, then the Director of the Center for Alternative Medicine Research and Education at Harvard Medical School (now of the Osher Center); these comments were met with appreciative laughter from the partisan audience. If such charges were valid, it would indeed be fortunate that Harvard Medical School, several other medical schools, and the National Center for Complementary and Alternative Medicine (NCCAM) are promoting homeopathy, both as a clinical method and as a topic worthy of research.

The inconvenient truth, however, is that for homeopathy and many other implausible health claims, Dr. Reilly was correct: controlled trials don’t work.

This will be a multi-part blog series that develops that argument.† In so doing it will expose a major weakness of Evidence Based Medicine: that its calculus does not incorporate plausibility in a useful way. It will also offer examples of hazards that result from this problem.

The History of homeopathy

The German Samuel Christian Hahnemann invented homeopathy in the late 18th century shortly before the proposal, by Avogadro, that would forever banish it to the realm of pseudoscience. In an effort to understand the widely-accepted efficacy of Peruvian Cinchona bark in the treatment of “intermittent [or ‘swamp’] fever,” Hahnemann took some himself:

I took by way of experiment, twice a day, four drams of good China (Cinchona). My feet, finger ends, etc., at first became cold; I grew languid and drowsy, then my heart began to palpitate, and my pulse grew hard and small; intolerable anxiety, trembling, prostration, throughout all my limbs; then pulsation in the head, redness of my cheeks, thirst, and in short, all these symptoms which are ordinarily characteristic of intermittent fever, made their appearance, one after the other, yet without the peculiar chilly, shivering rigor, briefly, even those symptoms which are of regular occurrence and especially characteristic – as the dullness of mind, the kind of rigidity in all the limbs, but above all the numb, disagreeable sensation, which seems to have its seed in the periosteum, over every bone in the body – all these made their appearance. This paroxysm lasted two or three hours each time, and recurred if I repeated this dose, not otherwise; I discontinued it, and was in good health. (2)

Hahnemann’s interpretation of this experience was that the elicitation of “symptoms which are ordinarily characteristic of intermittent fever” offered the key to the mechanism of action of the remedy. From this he deduced the “law” that gives homeopathy its name: the “law of similars.” This states that the best remedy for a condition is a substance that, when given to a healthy person, mimics the symptoms of the condition. Hahnemann’s singular experience with cinchona bark was the sole experimental basis for his first “law,” and it is still widely quoted in homeopathic literature that “Cinchona bark was to Hahnemann what the falling apple was to Newton and the swinging lamp to Galileo.” (3)

Science intervenes

Later it was discovered that quinine, an ingredient of Cinchona bark, has a specific anti-malarial effect. (4) The mechanism of action has been elucidated, and it has nothing to do with “like cures like,” vitalism, “dynamism,” or any other process proposed by Hahnemann or his followers. Nor does it have to do with host defenses, even those that are real. Thus the very foundation of homeopathy has been definitively disproved. It has recently been proposed that Hahnemann’s own experience was a hypersensitivity reaction to quinine. (5)

Hahnemann’s conclusion was not so unreasonable for its time, when most therapeutic hypotheses were based more on tradition and folklore than on science. “Like cures like” was a variant of the “sympathetic magic” theme common to the folk medicine of many cultures. (6) Contemporary explanations for the effectiveness of cinchona bark, one of the few useful remedies of the day, had to do with its “astringency” and its “tonic effect on the stomach.” (7,8) Neither these theories nor Hahnemann’s were close to the truth, but they can be forgiven for a time when medical science lacked molecular theory, physiology, pharmacology, or the germ theory.

Armed with his imagined insight, Hahnemann set about to investigate the proper uses of the pharmaceuticals of his day, by a process he called “provings.” This he did by taking substances himself or feeding them to his family, and noting the subsequent “symptoms.” (9) Many of these agents, e.g., arsenic and mercury, were highly toxic. Hahnemann eventually decided that the less that was used, the better the outcome. This decision, fortunate as it was for his children, led Hahnemann to formulate his second law: the “law of infinitesimals.” This states that the more dilute a preparation is, the more potent. The series of dilutions and shakings (“succussions”) that characterizes the preparation of every homeopathic “remedy” is known as “potentizing.” Ultra-dilute solutions are claimed to aid the body’s “vital force.”

Typical homeopathic preparations are diluted 1012-1060 times. Thanks to Avogadro, it can be calculated that dilutions much beyond 1023 contain nary a molecule of the original substance, or even any molecules of the diluent that had been in contact with the original substance, or any molecules of the diluent that had been in contact with that diluent, on ad infinitum. In addition, most completed “remedies” consist of a drop of diluent (water and/or alcohol) applied to a sugar pill and allowed to dry. Thus not only must any theory of action account for an increase in effect as the dilution approaches that at which none of the original substance remains, but it also must account for how such “memory” is amplified and transferred to multiple, further dilutions and ultimately retained by a sugar pill after the diluent has evaporated. It also must explain how the sugar pill lacks “memory” of any contaminants that may have been in contact with the diluent, among which must be every substance on the planet that has ever been in contact with water. Finally, such a remedy must act according to the first law of homeopathy, “like cures like,” the basis for which is known to be spurious.

The second “law” thus posits an incremental increase in the informational content of a preparation even as the original, purported source of that information, along with its fluid environment, progressively decreases to the point of nonexistence. This is incompatible with the facts of probability, of which information theory and the second law of thermodynamics are manifestations. Acceptance of Hahnemann’s own “second law” would require discarding evidence for the statistical nature of information decay that is tested and confirmed, in this era of electronics, countless times every millisecond. It would require overthrowing a universal law that Einstein called “the only physical theory…which I am convinced…will never be overthrown.” (10)